wc -l medals.txt
grep -E "中国|中国香港|中国台北" medals.txt | sort -t, -k2,2nr -k3,3nr -k4,4nr
sort -t, -k4,4nr medals.txt | head -n5 | cut -d, -f1
sort -t, -k2,2nr medals.txt | head -n5 | cut -d, -f2 | awk '{sum += $1} END {print "金牌前五的总数：", sum}'
